Usuall tapwater which is very soft. I have a layer of coral sand and crushed shells on the tank bottom to buffer the water. The pH is stable at about 8. I did the same for my empire gudgeons and bumblebee gobies. They eat anything and everything.

One interesting piece of behaviour – young specimens have an interesting (what I assume to be) predator avoidance tactic. If they are spooked they distort their body into weird positions (almost looks like they have broken backs) and just hang loose in the water column. Can be quite disconcerting when it first happens. After a minute or so they revert to normal.

@oaken said:
This is an awesome fish indeed. How big is the tank? And how do you collect their eggs? I seem to recall that this species deposits their eggs in crevices?

The tank is 3ft long and there are 15 fish in it. Today a friend is coming to take 6 which will leave enough room for the rest to grow a little more. They will need a larger tank in a couple of months though.

I put a rough sponge from a Fluval internal filter in the tank and they press their eggs into that.